This application claims the priority of German Patent Application Serial No. 100 18 595.9, filed Apr. 7, 2000, the subject matter of which is incorporated herein by reference.
The present invention relates, in general, to a coaxial cable connector, and more particularly to a coaxial cable connector of a type having a housing with a recess for receiving, contacting and clamping the end of the outer conductor of a coaxial cable, and with an inner conductor in the connector that contacts the inner cable conductor.
As disclosed in DE 42 06 092 C1, a particularly low intermodulation can be achieved by soldering the end section of a connector housing to the outer conductor of the coaxial cable. For soldering, the end section of the connector housing is positioned on the end of the outer conductor of the cable and heated, for example, heated tongs surrounding the end section of the connector housing or through induction. The solder in the form of a solder wire is supplied manually through bores in the end section of the connector housing into the gap between the inner wall of the recess of the end section of the connector housing and the outer conductor of the cable. This installation method for the connector on the cable requires special tools and considerable experience and can only be successfully done in the factory with cables having a maximum diameter of 13 mm ({fraction (1/2xe2x80x3)}). This makes it almost impossible to attain a connection with a low intermodulation by mechanically contacting and clamping at least the outer conductor of the cable in the field, i.e., during installation by the user and at the installation site.
For example, increasingly cables with a particularly low attenuation are required for mobile radio communications, in particular for connecting a mobile radio base station with a remote antenna installation. These cables can have an outer diameter of more than 60 mm and are for practical reasons typically fitted with the necessary connectors only at the installation site. With these connectors, at least the outer conductor of the cable is mechanically clamped in the end section of the connector housing. This process is not suitable for providing connections with low intermodulation. However, the marketplace increasingly requires field-installable connectors for even thicker cables which provide adequate intermodulation performance.
It would therefore be desirable and advantageous to provide an improved coaxial connector, which can be soldered in the factory as well as at the installation site, even for large-diameter coaxial cables for providing an optimal connection with low intermodulation.
According to one aspect of the invention, the inner diameter of the recess is identical to the smallest outer diameter of the outer conductor of the respective cable type and the wall of the recess has slots so as to be elastic in the radial direction.
Advantageously, the slots can extend parallel to an axial direction of the connector housing. The elastic segments in the portion of the connector housing which receives the end of the outer conductor compensate any tolerances in the diameter as well as deviations from the roundness of the outer conductor of the cable, which can be significant in particular when the outer conductors are corrugated. The various segments of the wall of the recess thereby contacts the outer conductor of the cable. Heat is then transmitted rapidly and uniformly from the wall of the end section of the connector housing to the outer conductor of the cable, and the supplied or existing solder melts quickly and essentially uniformly, with capillary action distributing the solder uniformly across the entire surface of the solder gap.
According to another feature of the present invention, a solder wire including flux agent is disposed on the wall of the recess in at least in the region of the nominal position of the front edge of the outer conductor of the cable. In this way, for cables with a smooth outer conductor as well as for cables with an annular or helical corrugated outer conductor, an amount of solder sufficient for filling the solder gap is provided and uniformly distributed along the circumference before the solder begins to melt. The soldering operation is thereby accomplished quickly without melting the dielectric of the cable.
If an inner conductor of the connector is to be soldered to the inner cable conductor, then the cable end is prepared for installation by having the inner cable conductor protrude over the end of the outer conductor of the cable by a distance that is equal to approximately two diameters of the inner conductor. in this way, the connection between the inner connector conductor and the inner cable conductor is established first. Subsequently, the end section of the connector housing is pushed over the cable, including the inner conductor of the connector, and subsequently heated to solder the end section of the connector housing to the outer conductor of the cable.
According to another feature of the present invention, the wall thickness of the wall recess at least in the receiving area of the outer conductor of the cable may be less than in the remaining region of the end section of the connector housing. This reduces the heat capacity of the end section of the connector housing in the area that is to be soldered, so that less heat has to be supplied and the solder operation takes less time.
Advantageously, the solder reservoir (reservoirs) is (are) disposed in a circumferential groove provided in the wall of the recess. This keeps the solder reservoir in place before the soldering operation and permits a smaller. the solder gap. Typically, two solder reservoirs that are separated in the axial direction are sufficient.
Suitably, round or slot-like recesses can be distributed along the circumference of the wall to allow visual observation of the solder process. The number and location of the recesses can be selected according to the circumference of the cable.
According to another feature of the present invention, the width of the slots can be so dimensioned that the solder flows into the slots through capillary action, independent of the exact position of the connector during soldering. The solder fills the slots uniformly after the soldering operation, so that connection between the end section of the connector housing and the outer conductor of the cable is sealed, both mechanically and against HF leakage.
According to another feature of the present invention, at least one additional solder reservoir can be disposed outside the wall of the recess at the height of the slots. The additional solder reservoir can have the form, for example, of an axial recess located in an annular shoulder of the wall that is filled with solder. The additional solder reservoir is recommended when the slots, which are located in the wall to provide sufficient radial elasticity, extend from the end section of the connector housing facing the cable a certain distance beyond the edge of the outer conductor of the cable towards the connector side. With this additional solder reservoir, even the region near the end portions of the slots will be completely filled with solder after the soldering operation.
According to another feature of the present invention, the wall can be surrounded by a solderable sleeve at least over a portion of the length of the slotted region. The sleeve is preferably located in a region of the end section of the connector housing that is located on the connector side of the front edge of the outer conductor of the cable. The sleeve increases the mechanical rigidity, in particular the bending stiffness, of the thin-walled region of the end section of the connector housing after the soldering operation, which functions as strained relief for the cable, absorbing tensile and bending forces. As mentioned above, the wall is kept thin to reduce the heat capacity. Depending on the diameter in this region, this sleeve can be slotted and snapped on or can be made of, for example, two suitably attached half shells. The quality of the solder joint can be inspected visually, if the sleeve leaves at least short sections of the slots unobstructed on the side of the connector and the cable.
The sleeve can be pressed onto the end section of the connector housing in a defined position, wherein the sleeve covers the slots in the wall at least over a portion of its axial extent, while still permitting the segments of the wall on the end section of the connector housing to become resiliently biased when the housing is pushed onto the outer conductor.
According to another feature of the present invention, the sleeve can contact a solder reservoir disposed in an outside annular ridge of the wall of the end section of the connector housing. The annular ridge defines the position of the sleeve.
Moreover, the sleeve can be non-positively connected with, in particular screwed on, the end section of the connector housing. The non-positive connection can be, for example, an outside thread formed on the end section of the connector housing engaging with an inner thread formed in the sleeve. The region with the non-positive connection need not be located in the same region of the end section of the connector housing where the outer conductor of the cable is soldered and the remaining regions of the slots on the cable side are filled. This sleeve can form the mechanical outer jacket of the end section of the connector housing and can also extend into the region of the connection plane. The sleeve can have an outside thread adapted to engage with a coupling ring of the mating connector. The sleeve also transmits tensile and compression forces acting on the cable and the connector.
At least at the height of the end portions of the slots, the sleeve can have a ring-shaped inner groove for receiving a solder reservoir. In this way, the slots in the wall of the recesses and the annular gap between the sleeve and the wall of the recess are completely filled with solder during the soldering operation. If the side of the sleeve facing the connector does not significantly protrude over the end portions of the slots and if the end face of the sleeve facing the connector is chamfered, then the flow of solder into the chamfer during the soldering operation due to the capillary action is indicative of a successfully completed soldering operation.
Each of the solder reservoirs or an additional solder reservoir can be provided as a solder foil between the surfaces to be soldered. The solder foil can also be located between the outer conductor of the cable and the corresponding inner wall section of the recess and/or between the wall of the end section of the connector housing and the sleeve.
Suitably, at least the inside of the wall of the recess can be wetted with a flux.
According to another feature of the present invention, at least the regions of the wall to be soldered, and more particularly the entire current-carrying surfaces of the end section of the connector housing, can be silver-plated.
In an embodiment of a connector adapted for helically corrugated cables, the wall of the recess can also be at least partially helical to complement the profile of the outer conductor of the cable, with at least one of the solder reservoirs conforming to the helical structure over at least a portion of its length. The other solder reservoirs can be ring-shaped, as for cables with smooth or helical outer conductors.
To further improve the intermodulation performance, the inner conductor of a connector can be adapted so that it can be soldered to the inner cable conductor.
In particular, the inner conductor of cables with a large diameter can be formed as smooth, ring-like or helical corrugated tube. In this case, the inner conductor of the connector can have slots that are elastic in the radial direction, with the inner conductor having least one solder reservoir to facilitate soldering. Providing the inner conductor of the connector with slots serves the same purpose as making the wall of the recess of the end section of the connector housing elastic in the radial direction. In this way, tolerances and roundness errors of the inner cable conductor can be compensated, while heat is transferred efficiently and rapidly from the inner cable conductor positioned on the outsidexe2x80x94through which heat is suppliedxe2x80x94to the inner conductor of the connector positioned on the inside.
Advantageously, the solder reservoir is made of ring-shaped solder wire including flux.
According to another embodiment, the wall of the end section of the connector housing can have openings through which molten solder can be supplied to the circumferential gap located between the outer conductor of the cable and the inner wall of the recess. The solder operation can also be visually monitored through these openings, wherein the number and location of the openings depend on the girth of the cable.